The present invention relates generally to devices used in intravascular therapeutic and diagnostic procedures, and more particularly, to a dilation balloon for a single operator exchange catheter.
Intravascular catheterization devices have proven to be useful and efficient for both therapeutic and diagnostic purposes. Intravascular therapeutic techniques, such as angioplasty, atherectomy, and laser irradiation, have been developed as alternatives to bypass surgery for treating vascular diseases or other conditions that occlude or reduce the lumen size of portions of a patient's vascular system. In particular, balloon angioplasty has proven to be a useful and in many circumstances a preferred treatment for obstructive coronary diseases. Also, intravascular diagnostic techniques, such as ultrasonic imaging and Doppler blood flow measurements, have been developed to measure or image the extent of an occlusion of a vessel (e.g. stenosis). The devices used to perform the aforementioned intravascular therapeutic and diagnostic techniques may be used together or in conjunction with more invasive techniques such as coronary surgery.
These intravascular therapeutic and diagnostic devices have achieved acceptance because of their effectiveness as well as the fact that they can be used in a minor surgical procedure that is relatively non-disruptive to the patient compared to coronary surgery. These devices rely on the positioning of a catheter into the vascular system of a patient via an incision at an accessible location which may be remote from the site of the occlusion or stenosis. For example, the accessible location may be the femoral artery at the groin. The intravascular device is then advanced through the incision via the femoral artery to a desired coronary distal site. The distal sites into which the device may be advanced include the coronary arteries, branch vessels stemming from the external carotid artery such as the occipital and the arteries leading to the vessels of the head and brain, splenic, and the inferior mesenteric and renal arteries leading to the organs of the thorax as well as other vessels.
Because of the small size of some of these vessels and the tortuous passages through the vessels, positioning of a catheter device through a patient's vasculature can be a difficult and time consuming task requiring considerable skill on the part of the physician. For example, in order to perform an angioplasty dilation, the angioplasty balloon catheter must be positioned across the stenosis in the arterial site. The stenosis may be located in a tortuous portion of the coronary vasculature and, furthermore, the obstructive arterial disease may impede crossing the stenosis with the balloon portion of the angioplasty catheter. Thus, not all arterial obstructions can be successfully treated by present intravascular balloon catheter procedures because some arterial obstructions are not readily accessible to a balloon dilation catheter. Accordingly, there is often a need for intravascular catheters of very low profile that can be positioned in narrow, tortuous regions of a person's vasculature.
Another important consideration relating to intravascular procedures, such as angioplasty, relates to the exchange of various devices used to perform the procedures. Intravascular therapeutic and diagnostic devices come in various types and sizes suitable for the vessel size and location in which the treatment is to be performed. Sometimes, it becomes necessary to exchange a first therapeutic device for one of a different size after an unsuccessful attempt has been made to position the first device in the appropriate location. It may also become necessary to exchange therapeutic devices after the first device is successfully positioned in the desired location. This may be necessitated because it becomes apparent that the first device is the wrong size or configuration, or because it is determined that additional therapeutic or diagnostic procedures with a different size or type of device is required.
Several different types of catheter constructions have been developed for positioning intravascular therapeutic or diagnostic catheters through a patient's vasculature. One type of catheter design, commonly referred to as a fixed-wire type catheter, includes a non-removable wire tip attached on a distal end of the intravascular catheter. The wire tip facilitates maneuvering the catheter to the desired vessel site. A disadvantage of the fixed-wire type catheter is that if it becomes necessary to exchange a first catheter for a second catheter, the maneuvering procedure must be repeated for the second catheter. As mentioned above, this can sometimes be a tedious and difficult procedure.
Another type of catheter design, referred to as an over-the-wire type catheter, includes a central lumen through the intravascular device that can accommodate a separate guide wire that is movable, and removable, in relation to the catheter to facilitate positioning the catheter in a remote vessel location over the guide wire. In the over-the-wire construction, the catheter typically includes a lumen adapted to receive the guide wire from a proximal end to the distal end of the device. The guide wire is initially loaded through the lumen of the over-the-wire catheter and extends out from the distal end thereof. Then, the guide wire and the intravascular catheter are advanced together and positioned in the vessel at the desired site. The guide wire may be advanced distally of the distal end of the catheter and steered, as necessary, to traverse tortuous passages of the vessel. The guide wire may then be withdrawn proximally through the lumen of the catheter or may be left in place extending from the distal end of the catheter during the procedure.
The over-the-wire type intravascular catheter facilitates exchanges because a first catheter can be exchanged with a second catheter without removing the guide wire. This allows an exchange of catheters without having to repeat the difficult and time consuming task of positioning the guide wire. In order to leave the distal end of the guide wire in place, it is preferred to maintain a hold on a proximal end portion of the guide wire during the exchange operation. One way to maintain such a hold is to use a guide wire having a sufficiently long length (e.g. 300 cm) so that the entire catheter can be completely withdrawn over the guide wire while maintaining a hold on a portion of the wire. A disadvantage of this method is that the long proximally extending portion of the guide wire may be in the way during the procedure. Another way to maintain a hold on a portion of the guide wire during an exchange operation is to use a guide wire extension. A disadvantage of this method is that not all guide wires are adapted to connect to an extension wire, and moreover, the step of connecting the guide wire to the extension wire can sometimes be tedious and difficult to perform.
A variation of the over-the-wire type catheter which facilitates the exchange a first catheter with a second catheter is the single-operator exchange type construction. With the single-operator exchange type construction, a guide wire occupies a position adjacent and exterior to the intravascular catheter along proximal and middle portions of the catheter. Typically, the guide wire enters into a guide wire lumen which is attached to a shaft of the catheter and often extends through the balloon. With this type of construction, the catheter can be positioned in the patient's vessel by positioning a guide wire in the desired location and advancing the catheter device over the wire. In the event it becomes necessary to exchange the catheter, the position of the guide wire can be maintained during withdrawal of the catheter without the use of a long guide wire (e.g. 300 cm) or an extension wire. Because the proximal end of the guide wire is exterior to the catheter, the guide wire can be held during withdrawal of the catheter so that the position of the distal end of the guide wire in the patient's vessel can be maintained. With this type of catheter, it is desirable to minimize the length of the guide wire lumen to decrease frictional forces acting on the guide wire, thus facilitating the trackability of the catheter over the guide wire. One disadvantage of some single-operator exchange type devices is the increased profile of the balloon resulting from a separate guide wire lumen extending therethrough. As noted above, it is desirable to minimize the profile of the balloon to allow positioning in narrow, tortuous regions of a person's vasculature.
With both fixed wire and over-the-wire type catheters, an introducer sheath and/or a guiding catheter may also be employed. An introducer sheath is used to provide translumenal access to the femoral artery or another appropriate location. Then, with the access provided by the introducer sheath, a guide catheter may be positioned in the patient's vessel. The guide catheter may be advanced at least part of the way to the desired site, such as to the aortic arch. The guide catheter has an internal lumen through which the intravascular device, including the guide wire in an over-the-wire construction, is advanced. One of the functions of the guide catheter is to support the device. The guide catheter may be approximately 100 to 106 cm in length. Alternatively, in certain situations, e.g., if positioning of the device does not involve traversing tortuous vessel passages, a guide catheter may be employed to position an intravascular device without the use of a guide wire.
Accordingly, there is a need for an improved single-operator exchange type catheter which minimizes the profile of the balloon and facilitates trackability of the catheter over the guide wire.